What are the products of reactions of hydrocarbons and how do they react?

Question 1

Why are alkanes good fuels?

Answer 1

they are fairly stable but still burn readily in an exothermic reaction.

Question 2

what common fuels contain mixtures of alkanes and other hydrocarbon molecules ?

Answer 2

petrol, diesel and kerosene

Question 3

what is the main component of natural gas?

Answer 3

methane- the simplest alkane

Question 4

what are the products of burning hydrocarbon fuels in excess oxygen?

Answer 4

carbon dioxide and water vapour

Question 5

what happens in a substitution reaction?

Answer 5

when an atom or functional group in a molecule is replaced or substituted by another

Question 6

how must a reaction vessel at room temp and in the dark, containing a mixture of an alkane and chlorine gas react?

Answer 6

the reaction must be initiated by ultraviolet light (UV)

Question 7

write out the reaction between methane and chlorine

Answer 7

(reference pg 312)

Question 8

for each molecule of chlorine gas (Cl2) that reacts……

Answer 8

a hydrogen atom on the alkane is replaced by a chlorine atom.

Question 9

why are alkenes more reactive than alkanes?

Answer 9

because they are unsaturated and they have a double bond.

Question 10

what affect does the double carbon-carbon covalent bond in alkenes have on its chemical properties?

Answer 10

alkenes will generally react more readily and with more chemicals than alkanes.

Question 11

what happens in an addition reaction?

Answer 11

the addition of a small molecule to the double bond of the alkene

Question 12

what changes are made to the alkene in an addition reaction?

Answer 12

two products are formed into one, the double bond becomes single, the unsaturated compound because saturated and the atoms of the small molecule are added across the double bond.

Question 13

write out the reaction between ethene and hydrogen bromide. what is the product?

Answer 13

(reference pg 313) the only product is bromoethane

Question 14

what four different types of addition reactions do alkenes undergo?

Answer 14

reaction with: hydrogen, halogens, hydrogen halides and water

Question 15

how do alkenes and hydrogen gas react?

Answer 15

in the presence of a metal catalyst: nickel

Question 16

what is the reaction of an alkene and hydrogen gas called ?

Answer 16

hydrogenation reaction

Question 17

write out the hydrogenation of ethene with hydrogen gas

Answer 17

reference pg 313

Question 18

write out the addition reaction of ethene and bromine

Answer 18

reference pg 314

Question 19

how do the reactions of alkenes and halogens occur?

Answer 19

at room temperature without a catalyst

Question 20

why is bromine often used as a test for the presence of a carbon-carbon double bond?

Answer 20

because of the ease and speed with which it reacts with an alkene

Question 21

what happens when an alkene is added to aqueous bromine?

Answer 21

the alkene reacts with the coloured bromine and the solution loses colour

Question 22

what happens when an alkane is added to aqueous bromine?

Answer 22

no addition reaction occurs so there is no colour change

Question 23

what are hydrogen halides?

Answer 23

chemical molecules that contain one hydrogen atom and one halogen atom.

Question 24

write out the reaction between the alkene but-2-ene and the hydrogen halide, hydrogen chloride

Answer 24

reference pg 314

Question 25

write out what happens when you react hydrogen chloride and but-1-ene

Answer 25

reference pg 314- two isomers are possible as products

Question 26

what happens in a reaction of an alkene and water?

Answer 26

under specific conditions, alcohol is produced

Question 27

what is the molecular formula for sulphuric acid?

Answer 27

H2SO4

Question 28

what is the molecular formula for phosphoric acid?

Answer 28

H3PO4

Question 29

write out the reaction of ethene and water using a catalyst to increase rate of reaction to produce ethanol

Answer 29

the addition reaction of steam and ethene using a sulphuric acid or phosphoric acid catalyst.

Question 30

what is a hydration reaction?

Answer 30

reactions that involve water as a reactant

Question 31

why is the reaction of ethene and steam to produce ethanol used for commercial manufacture ?

Answer 31

because it is a one-step process that uses little energy and the heterogeneous nature of the reaction system means it is easy to remove the product from the reaction mixture.

Question 32

write out the reaction of propene with water in the presence of dilute sulphuric acid

Answer 32

two isomers are possible products: propan-1-ol and propane-2-ol

Question 33

what is needed for the reaction between alkenes and water?

Answer 33

the presence of a high amount of acid with catalytic effect

Question 34

why is ethene such an important chemical?

Answer 34

since it is an alkene, it undergoes addition reactions that convert alkenes into a number of substances. ethene is so useful because it can be used as a starting material (feedstock) from which other substances can be made.

Question 35

what are the 3 steps in a hydrogenation reaction?

Answer 35

1. hydrogen molecule react with the metal catalyst, forming two weak metal-hydrogen bonds.
2. alkene molecule reacts with the metal catalyst and the double bond breaks into a weak metal-hydrogen bond
3. the metal catalyst causes the hydrogen atoms to join to the carbon atoms, creating the final molecule.

Question 36

why is there no catalyst needed in a hydrogen halide addition reaction?

Answer 36

no catalyst is needed due to the reactivity of halogens.

Question 37

what is the reaction between water and an alkene, and what is its catalyst?

Answer 37

water is added across the double bond using dilute H2SO4 as a catalyst, where the alkene becomes and alcohol. (hydrogenation)

Question 38

what os the reaction between water and an alkyne, and what is its catalyst?

Answer 38

water is added across the triple bond using mercury (II) compounds and sulphuric acid. the addition of water will produce a ketone. (except for ethyne)